Failover is a technique for improving reliability of storage apparatuses. In failover, a plurality of storage apparatuses is clustered. For example, while one of the storage apparatuses is performing an operation, if the storage apparatus goes down because of a malfunction of a device therein, another storage apparatus is allowed to take over the ongoing operation. There is also a technique referred to as transparent failover (TFO).
In TFO, an apparatus (a host) such as a server accessing storage apparatuses is not notified of occurrence of failover. TFO may be set per logical volume, and another storage apparatus is automatically allowed to take over the input and output (I/O) of a data writing and reading operation performed by a malfunctioning storage apparatus. In this operation, the user is allowed to continue the ongoing operation without being conscious of occurrence of failure. In addition, the recovery time is reduced and the storage administrator's work burden is reduced.
Volumes used in TFO (hereinafter, TFO volumes) are seen by a host as a single volume. This is realized by using, for example, target port group support (TPGS) and connecting a plurality of storage apparatuses to the host via respective paths (communication paths). In such case, common small computer system interface (SCSI) unique ID (Inquiry VPD page #83) of the devices are used among the clustered storage apparatuses, and a path used by an operating storage apparatus is set to “Active” and a path used by a standby storage apparatus is set to “Standby.” The host is only allowed to access the operating storage apparatus via the “Active” path. When the operating storage apparatus goes down, the standby path is changed to the “Active” path. In this way, the I/O of a data writing and reading operation is automatically taken over by the storage apparatus connected to the host via the path that has been changed to “Active.”
As a technique relating to clustering of storage apparatuses, for example, asynchronous remote copy that is performed in conjunction with a storage clustering technique is being considered. In addition, a technique relating to failover recovery between storage systems using virtual volume modules is also being considered.
See, for example, the following documents:    Japanese Laid-open Patent Publication No. 2011-76130    Japanese Laid-open Patent Publication No. 2006-48676
When data in a TFO volume is operated, there are cases where logical unit numbers (LUNs) in a storage apparatus are specified, instead of device names commonly set among the storage apparatuses. A LUN is an identification number used for identifying a storage device in a storage apparatus. For example, when a host operates a TFO volume, the host converts the device names of the operation target into the corresponding LUNs, to specify the operation target.
Normally, when data in a TFO volume is operated, the operation target is specified with device names. If the operation target is specified with device names, while the device names need to match device names of a plurality of storage apparatuses forming a TFO volume, the LUNs of the storage devices in the “Active” storage apparatus do not need to match those of the storage device in the “Standby” storage apparatus. To match these LUNs in the “Active” and “Standby” storage apparatuses, the administrator needs to change configurations of the storage apparatuses. Namely, the administrator's burden is significantly increased. Thus, under the present circumstances, even when storage devices have an active-standby relationship, the LUNs are not matched in most cases.
However, when data is operated by specifying the LUNs of a TFO volume as the operation target, if TFO is executed, since the LUNs of the volumes in the “Active” and “Standby” storage apparatuses do not match, an erroneous storage device is specified after TFO.